Select column A first, then create a new conditional format and select "Use Formula ..."

Then enter the formula in the input box:

=RANK($A 1，A:A)= 1

Set the format to red and confirm.

Continue to create a new conditional format in the same way, and the formula is:

=RANK($A 1，A:A)=2

=RANK($A 1，A:A)=3

=RANK($A 1，A:A)=4

……

Set the corresponding color.